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VISUAL IMAGERY AND ATTENTION 
AN ANALYTICAL STUDY 

BY 

HELEN CLARK 
A. B. Vassar College, 1913 



THESIS 

Submitted in Partial Fulfillment of the Requirements 
for the Degree of 

DOCTOR OF PHILOSOPHY 
IN PSYCHOLOGY 



IN 

THE GRADUATE SCHOOL 

OF THE 

UNIVERSITY OF ILLINOIS 
1916 



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CONTENTS 

I. Introduction 1 

II. Experimental: An Analysis of Visual Imagery. ...... 4 

III. Experimental: Imagery, Ocular Movement, and 

Attention 14 

Experiment 1 14 

Experiment 2 20 

Experiment 3 23 

Experiment 4 36 

IV. Summary and Conclusions 42 



VISUAL IMAGERY AND ATTENTION: AN ANALY- 
TICAL STUDY 1 



By Helen Clark 



I. Introduction 

Ever since the appearance of Galton's " Inquiries into 
Human Faculty," 2 the subject of imagery has received, almost 
constant attention from psychologists, and, moreover, its culti- 
vation has been strongly marked by an increasing diversity 
of new problems. It is not necessary to pass the general 
literature of the subject in review; but we shall briefly men- 
tion those phases of it which are most closely related to the 
present study. First of all, we must note that the current 
tendency to view mind in its historical aspects has prompted 
the psychologist to seek for the antecedents of the image; 
to discover, that is to say, its dependence upon perception. 
Experimentalists now generally " incline to the view that 
there is no intrinsic difference between sensation and image." 3 
Investigations in the field of suggestion reveal the fact that, 
under certain circumstances, simple or total images may be 
mistaken for sensations or perceptions. 4 On the other hand, 
" a visual perception of distinctly supraliminal value may 
. pass — even with specially trained observers — for an 
image." 5 Related studies have dealt with the development 
and the decay of imaginal complexes in the course of time. 
The associationists' conception of stable psychical enti- 
ties has been discarded, and the view commonly held at 
present is that " the memory is not to be regarded as a store- 
house of perfectly conserved images, but that the most simple 
memories are continually exposed to change, and that it is, 
at times, only by the combination of various memorial re- 

1 From the Psychological Laboratory of the University of Illinois. 

2 Galton, F., Inquiries into Human Faculty and its Development, 
1883. 

3 Perky, C. W., An experimental study of imagination, Amer. J. 
of Psychol, 1910, xxi, 435. Cf. Kiilpe, O., Philos. Stud., xix, 5o8ff., 
and Washburn, M. F., Mind, n. s., viii, 1899, 32. 

4 Cf . Seashore, C. E., Measurements of illusions and hallucinations 
in normal life, Studies from the Yale Psychological Laboratory, 1893- 
97, i-v, 32. 

5 Perky, op. cit., p. 435. 



S 



462 CLARK 

sources that retention is made definite and exact." 6 Experi- 
mental and theoretical inquiries have also been directed toward 
the general functions of the image in relation to thought and 
meaning, 7 discrimination and judgment, 8 and reproduction 
and recognition. 9 Moreover, there have been several attempts 
made at classification of total images on a basis of divers char- 
acteristics, usually functional. Visual images have here re- 
ceived most consideration. Four important investigations 
which have recently appeared are those of Perky, 10 L. J. Mar- 
tin, 11 K. Koffka, 1 ^ and R. M. Ogden. 13 And finally, images 
have been studied in their relations to motor phenomena, espe- 
cially to ocular movement. 141 

The problems and methods in Ogden's and in Perky's in- 
vestigations closely resemble those of our own experiments. 
There are, however, three important differences, (i) Both 
Ogden and Perky discovered a number of intermediate or 
" equivocal " images 15 which did not seem to belong either 
among their " images of imagination " or with their " images 
of memory." We decided to include in our classification all 
non-verbal (or primary) images which were reported by our 
observers. (2) As regards ocular movement, Ogden obtained 
negative results (p. 381) ; while Perky, by means of another 
procedure, discovered a striking correspondence between the 
kind of image and the occurrence of ocular movements (pp. 

6 Bentley, M., The memory image and its qualitative fidelity, Amer. 
J. of Psychol., 1899, xi, 47L Cf. Philippe, J., L'image mentale; evolu- 
tion et dissolution. Paris, 1903, 76ff, u6f. 

7 Cf . Betts, G. H., The distribution and functions of mental imagery. 
Teachers College, Columbia University, 1909, p. 41. 

8 Cf . Whipple, G. M., An analytical study of the memory image and 
the process of judgment in the discrimination of clangs and tones, 
Amer. J. of Psychol., 1901, xii, 409ff. 

9 Bentley, M., op. cit., 46. 

10 Op. cit. 

11 Die Projecktionsmethode und die Lokalisation visueller und an- 
derer Vorstellungsbilder, Zsch. f. Psychol, 1913, lxi, 321. 

12 Zur Analyse der Vorstellungen und ihrer Gesetze, Leipzig, 1912. 

13 "Experimental criteria for differentiating memory and imagination 
in projected visual images, Psychol. Rev., 1913, xx, 378. 

< 14 Perky, op. cit., and Ogden, op. cit. Cf. Meakin, F., Mutual inhibi- 
tion of memory images, Harvard Psychological Studies, i, 1903, 244; 
Moore, C. S., Control of the memory image, ibid., 296; Slaughter, J. 
W., Behavior of mental images, Amer. J. of Psychol., xiii, 1902, 548; 
Kuhlmann, F., Analysis of the memory consciousness, Psychol. Rev., 
xiii, 1906, 338f ; Murray, E., Peripheral and central factors in memory 
images, Amer. J. of Psychol., xvii, 1906, 241 ; Kiilpe, Outlines, 1909, 
187; Burtt, H. E., Factors which influence the arousal of the primary 
visual memory image, Amer. J. of Psychol, xxvii, 1916, 87. 
15 Ogden, p. 406; Perky, 436. , ' ■ 



VISUAL IMAGERY AND ATTENTION 463 

442, 451). We decided to observe movements of the eyes 
by three different methods, one of them being somewhat simi- 
lar to Perky's. (3) We proposed to discover, if possible, 
the factor or factors most closely connected with ocular move- 
ments, not simply the sort of image which was usually 
involved. 16 

Before proceeding to the account of our experiments, we 
must observe that the term " image " is ambiguous. As it is 
used by psychologists to-day, it stands for (1) a mental pro- 
cess, (2) a group or constellation of mental processes, (3) 
a kind of reference or meaning, and (4) a particular sort or 
class of objects. As regards the first two meanings, we shall 
distinguish the "simple image" (a single imaginal process 
taken at the level of sensation and affection) from the " total 
image " (the single imaginal constellation or complex) ; and 
so far as the functional treatment of imagery is concerned, — 
the treatment which discovers such marks as " particularity," 
" locality," and " personal reference," — we shall try to make 
clear in the context when we are dealing with meanings and 
objects and when we intend to indicate processes. The attempt 
is worth while because it is still frequently assumed, even 
by serious writers, that the imaged object is a " mental " 
object and so ultimately different for the psychologist from 
the physical objects of perception. 

II. Experimental: An Analysis of Visual Imagery 

Problem and method. Our first investigation was an analy- 
tical study of the visual images aroused by a series of words. 
The purpose of the experiment was to obtain a descriptive 
account of the images evoked with respect to twelve different 
characteristics, to classify the images with reference to two 
of these peculiarities, and to discover whether there was a 
resemblance in other details among the images of each group. 

There were two observers, A and B. 17 was seated in a dark 
room facing a black wall. The experimenter took her place behind 
the observer at a table provided with a shaded light for the recording 

36 Our observers, named in the order in which they served in the 
experiments, were : an advanced undergraduate — Miss B. V. Copley 
(A) ; two graduate students— Mr. C. E. Holley (B), and Miss A. S. 
Rogers (C) ; three instructors in psychology — Dr. C. A. Ruckmich 
(D), Dr, J. E. DeCamp (E), and Dr. C. Rahn (F). The author 
wishes to express her grateful appreciation of their services and to 
acknowledge her especial indebtedness to Professor Bentley, under 
whose supervision the investigation was pursued. 

17 " o " has been used in the following pages as an abbreviation for 
"observer." ; . 



464 CLARK 

of O's descriptions. The experimenter transcribed O's account as O 
dictated. For evoking the images, 114 substantives were used with A; 
with B, 75 words taken from the same list. 18 The instructions were 
as follows : " After a signal ' ready,' I shall pronounce a word. You 
are to note any visual image that may occur. As soon as it has dis- 
appeared, give a full description of it." 

It is to be observed that the instructions were quite general. The 
subject was not required to call up an image, but merely to note any 
that should occur. Furthermore, the image was not supposed to be 
that of a particular object, but simply any visual image. The subject 
was not asked voluntarily to hold the image, which was to take its 
natural course. 

The description was not interrupted; but, when O had finished his 
account, he was questioned as to any points which he had overlooked. 
The experimenter sought complete information concerning (1) spe- 
cificity of reference ("particularity"), (2) familiarity, (3) the posi- 
tion of the imaged object in relation to O, (4) the visual background, 
(5) the size of the imaged object, (6) its stability, (7) the number and 
the degree of clearness of its details, (8) color, (9) accompanying 
affective tone, (10) somatic reference, (11) associative processes, and 
(.12) temporal reference. 

Results. The images reported were first divided into three 
main groups. Those which referred to specified objects and 
which were apprehended as familiar were called F-images. 
Memory images (those which not only referred to specified 
objects and were apprehended as familiar, but which also 
involved a reference to a particular place and to O's past ex- 
perience), were considered as a sub-class of the F-images. 
Images which were specific and unfamiliar were called U- 
images. These were not necessarily accompanied by a feeling 
of strangeness ; there was, in most cases, merely absence of 
familiarity. Finally, images of general reference (signifying 
a class or a member of a class of objects), which also involved 
no familiarity, were designated as G-images. 19 With regard 
to position, the imaged objects were classified as usual when 
they had the same position in relation to the observer as the 
perceptual objects commonly occupied; they were called 
unusual if the position was not characteristic of the perceptual 
object, or if the imagined object seemed detached from any 
setting, or if the localization was extremely indefinite. Images 
were classified as unstable if they fluctuated, faded quickly, 
or were soon replaced by other images. When describing the 

18 Some of the words were : knife, river, dog, church, soap, cloud, 
grass, king, lyre, Cerberus, druid, tournament, King Arthur, wand, 
nightingale, baron, Marmion. 

19 Both the generality of reference and the definiteness of spatial 
orientation we found, as did Koffka, to present a large number of 
degrees and gradations. These differences seem, however, to be unim- 
portant for our main purpose. 



VISUAL IMAGERY AND ATTENTION 465 

details of images as many or few, the experimenter took into 
consideration the amount of detail which corresponding objects 
revealed in perception. Color was described as absent if color 
was normally present in the perceptual mode of the object. 
We took associative processes to mean relevant processes not 
completely assimilated to the total image. Such associative 
processes might occur at the same time as the principal image, 
although they were more apt to appear subsequently. Where 
the corresponding perception had occurred at some time within 
a year, the image was classed as recent. Somatic reference 20 
was present in several forms. In some cases, the observer 
simply was at the place presented in imaginal form. 

" The church was in the position in which it would be if I were 
walking up to it." "Then the image changed, as I went inside." "I 
was there. I seemed to be younger than I am now." " I was lying on 
my back and looking at the clouds." 

Some images stood in definite relation to certain parts of 
the body. 

" The gun was parallel to my arm as though my arm were extended." 
"The bird was back of my arm at the left. I thought of turning my 
head and looking at it." " The shoes were on my own feet." 

In some cases, the somatic reference was more explicit. 

" I imagined myself as there." " I seemed to be coming along the 
walk." " I knew that I was there." 

In one case, the subject had a definite visual image of 
herself. 

" I saw myself take the key out of the rubber where it is kept." 

20 The word " somatic " is used to avoid the ambiguous term " per- 
sonal." Perky uses, without definition (p. 436), "personal reference" 
as one of her two cardinal distinctions between " images of memory " 
and " images of imagination." We mean by " somatic reference " that 
the observer apprehended the imaged object as related to his own per- 
ceived or imaged body. The words " personal reference " might have a 
similar significance; but they might also imply a reference to the ob- 
server's past experience. Our own analyses seem to indicate that " par- 
ticularity," Perky's second cardinal distinction, is — even when taken 
with the first — an unsatisfactory mark of memory. We found many 
particular and specified objects which could not, save by v the most arbi- 
trary designation, be called " memories." Similar criticism upon these 
terms has been passed by Koffka (p. 226) and Ogden (p. 384ff). 
Perky's determination to study " imagination " appears to have in- 
duced her to accept, without refined analysis, a " rough and ready cri- 
terion " of the simpler imaginal complexes. Although she uses this 
criterion "for preliminary purposes" (p. 451), it nevertheless deter- 
mines her whole conception of the simpler processes and modes of 
integration by which, as she assumes, "imaginations" are built up. 



466 



CLARK 



All of these functional distinctions are, of course, more or 
less crude. They should, however, suffice to reveal any strik- 
ing dissimilarities existing among our classes. 

Table I shows the distribution of the different kinds of 
images for each observer. 



TABLE I 



Observers 


F-i mages 


G-images 


U-images 


Totals 


Primary 


Primary 


Secondary 


Primary 


A 


36 


61 




43 


140 






B.. 


36 


12 


7 


4 


59 






Totals 


72 


73 


7 


47 


199 







Most of the visual images were primary (non-verbal), but some of 
B's images were secondary or symbolic (verbal). The 7 secondary 
visual images mentioned in the table appeared as independent total 
images. They are not included in the following discussion of results 
unless specifically mentioned. 

Table II shows a more detailed analysis of the images. As 
regards the temporal relations of the F-images, over half 
(53%' an d 61%) were referred to objects seen habitually and 
recently (within a year), while more than a third (36% and 
39%) referred to objects perceived on some recent and specific 
occasion. In 11% of A's F-images there was recognition 
without definite temporal relations. Under three of the prin- 
cipal headings of classification there seemed to be little or no 
correspondence between the kind of imagery and a particular 
characteristic. These headings were color, stability, and size. 

1. Color was present in all but six images. Three of these 
were F-images, one was a G-image, and one was a U-image. 

2. Stability was characteristic of 61% of A's F-images, but 
only 39% of B's F-images were stable. Of B's G-images 
83% were unstable. In the other cases, the percentages are 
not significant. 

3. Normal size was reported in from 70% to 100% of the 
cases in each group. In the case of A, the G-images char- 
acterized by abnormal size were three times as numerous as 
the corresponding F-images, while the abnormal U-images 
were four times as numerous as the F-images. Of B's images, 
on the other hand, the F's were the only ones that were ever 
characterized by abnormal size. These reports, however, may 



VISUAL IMAGERY AND ATTENTION 



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468 CLARK 

be significant when considered in another connection. 21 Table 
III shows that it was usually the images of large objects that 
were under-sized and also those of small objects that were 
over-sized. 

TABLE III 



Images of 


Exaggerated 


Dwarfed 


Small objects 


10 


1 








2 








Large objects 


3 


16 







The small objects which were exaggerated when imaged were a 
picture of Queen Elizabeth, a pin, a lemon, a key, a cake of soap, a 
dinner favor, a tomato, a maple leaf, and two flies. The image of a 
snake was under-sized. The two medium-sized objects which were 
exaggerated in imagery were a coat and a bag. Of the large objects, 
a king, a giraffe, and Ceres were exaggerated, while a tower, a valley, 
a castle, a horse, a temple, a tabernacle, King Arthur, a crusader, a 
baron, a serf, Marmion, the Delphic oracle, the Nile, and three forest 
scenes were under-sized when imaged. With 15 of the 17 images that 
were dwarfed there was a visual background. With 11 of the 15 that 
were exaggerated there was no visual background or only a shade or 
haze, while in 2 more cases the scene was vague. 

Objects of a certain size are probably perceived with less 
effort than objects or scenes considerably larger or smaller. 
Perception of the small objects may involve unpleasant mus- 
cular strain resulting from the convergence of the eyes. This 
is especially true when the object is close to the observer. 
Large objects or scenes necessitate considerable ocular move- 
ment if all the different details are to be clearly perceived. 
In some cases, images seem to show a tendency to take that 
size which, in actual perception, would involve the least ocular 
strain. 

Although the three kinds of images did not present marked 
differences as regards color, stability, and size, certain other 
peculiarities were more characteristic of one sort of imaged 
object than of another. We distinguish six cases. 

21 J. M. Baldwin and W. J. Shaw (Memory for square size, Psychol. 
Rev., ii, 1895, 236) found that the size of comparatively small objects 
was over-estimated. H. K. Wolfe (Some judgments on the size of 
familiar objects, Amer. J. of Psychol, 1898. ix, 137) discovered that 
familiar objects (e. g., bank-notes) were under-estimated when drawn 
on paper. In criticism of this experiment it has been said that " this 
fact does not necessarily report the visual image of the note,, since 
reproduction might easily be biased by the introduction of alien senses, 
i. e., pressure, muscular exertion, etc." (M. Bentley, The memory 
image and its qualitative fidelity, Amer. J. of Psychol., 1899, xi, 1.) 



VISUAL IMAGERY AND ATTENTION 469 

i. The F-images occupied a "usual" position (89% and 
97%) ; the U-images not quite so frequently (84% and 75%). 
A's G-images were less apt to occupy a usual position (61%), 
and, in the case of B, the position was even less likely to be 
usual (33%). 

2. The visual background in 83%' and 87% of the F-images 
and in 67% and 50% of the U-images was a scene. On the 
other hand, there were scenic backgrounds in only 35% and 
8% of the G-images. 

3. The details of the images were both many and clear 
in 72% (A) and 31% (B) of the F's and in 60% (A) and 
25% (B) of the U's. The details were few and vague in 
29% (A) and 92% (B) of the G-images. 

4. Somatic reference occurred with 64% and 61% of the 
F-images, but with only 11% and 8% of the G-images and 
with 14% and 50% of the U-images. 

5. Associative processes were present with a considerable 
number of U-images (67% and 50%), with a smaller number 
of F-images (36% and 36%), and with still fewer G-images 
(15% and 25%). 

6. As regards affective tone, F-images were often accom- 
panied by pleasantness (72% and 47%), U-images were less 
frequently associated with pleasantness (63% and 25%), 
while with G-images consciousness was even less often pleas- 
ant (44%' of A's images) and might be predominantly neutral 
in tone (100% of B's images). B reported no cases of un- 
pleasant affective tone. Of A's 140 images, 32 were connected 
with unpleasantness. In 17 of these cases, however, the un- 
pleasantness might be explained by the nature of the object 
imaged, while in 6 other cases the unpleasant tone is to be 
referred to associative connections. Only two images involved 
a definite feeling of strangeness or unfamiliarity. One of 
these was accompanied by pleasantness, the other by unpleas- 
antness. These results would seem to show that images re- 
ferring to agreeable experiences are more apt to be recalled 
than are those referring to the disagreeable. 22 

22 The belief that there is a tendency to forget the disagreeable is 
held by Colegrove (Memory, 1900, n), Freud (Zur Psychopathologie 
des Alltagslebens, 1907), and Hollingworth (The oblivescence of the 
disagreeable, /. of Phil, Psychol, etc., 1910, vii, 709). This view is 
questioned by E. N. Henderson (Do we forget the disagreeable? ibid., 
191 1, viii, 432), who found that one-third of the memories of ten 
observers were disagreeable. He considers it possible that the average 
person actually has more pleasant than disagreeable experiences, and 
that an incident which is remembered with pleasure might really have 
involved unpleasantness when it occurred. " We forget not so much 
disagreeable ideas as useless ideas." 



470 



CLARK 



A certain combination of characteristics might be regarded 
as peculiar to the pure type of each sort of image. The pure 
F-image may be distinguished by its usual position, its scenic 
background, many clear details, a pleasant affective tone, 
somatic reference, and associative processes. The pure G- 
image is in an unusual position and has no background, or 
merely a shade or haze as background, few and vague details, 
a neutral affective tone, no somatic reference, and no asso- 
ciative processes. Like the F-image, the pure U-image has 
a usual position, a scenic background, many clear details, a 
pleasant affective tone, and associative processes; but it has 
no somatic reference. If, however, one attempts to classify 
the individual images under these detailed headings, it is evi- 
dent that there are very few examples of the pure types and 
many deviations from them. 

Table IV summarizes the variations of the images from 
the pure types. Only 17 of the whole number are " pure " 
under our definitions, while 48 vary from the " type " in one, 
and 68 in two particulars. Transition from one class to an- 
other was shown in various ways. Let us illustrate. In con- 
nection with one image there was a feeling of familiarity, but 
the observer was unable to place it in any spatial or temporal 
relations. In other cases there was no recognition, though 
scenes associatively appeared which the observer thought 
might possibly have been the original settings of the object. 
In four cases recognition occurred after the image had begun 
to fade. vSeveral G-images and one U-image had as back- 
grounds scenes that were recognized. Once the image re- 
mained the same while one scenic background was replaced 
by another. In 44 cases the pronunciation of the word was 

TABLE IV 





A's Images 


B's Images 




F-Im. 


G-Im. 


U-Im. 


F-Im. 


G-Im. 


U-Im. 




4 


1 


7 


1 


4 









Variant in 

1 characteristic 


11 


13 


10 


9 


5 




2 characteristics 


14 


16 


15 


19 


3 


1 


3 characteristics 


4 


15 


10 


4 




1 


4 characteristics 


1 


13 


1 


23 




2 


5 characteristics 


1 


3 










6 characteristics 


1 






1 







VISUAL IMAGERY AND ATTENTION 471 

followed by two successive total-images. Of these successions 
nine were from one G-image to another of the same sort, nine 
were from an F-image to another F-image, and nine were 
from a G-image to a representative of the F class. In 13 
cases, images from other sense departments were assimilated 
to the total image. Five of these were temperature-tactual 
images, 5 were kinaesthetic-tactual, 2 were olfactory and 
one was auditory. 

So far as it is permissible to base general conclusions upon 
our material, these results seem to indicate that, although 
visual images may be classified according to their genesis or 
function, there are no definite groups which show peculiar pat- 
ternings of the ten characteristics, intrinsic and functional, 
which we have mentioned. Individual differences are consid- 
erable, and intermediate images are very numerous. F-images, 
G-images, or U-images may, perhaps, best be considered as 
designating various points in a developmental or an elaborative 
series, rather than sharply differentiated classes. 

III. Experimental: Imagery, Ocular Movement and 
Attention 

Experiment 1 

Problem and method. The purpose of this experiment was 
to discover whether there exists any connection between the 
general character and functions of the visual image and the 
occurrence and extent of ocular movements. A and B again 
served as observers. The observer was seated in the dark 
room with his head fixed in a head-rest. A sheet of blank 
cardboard was placed at the distance of a meter from his 
eyes so that a white fixation-point appeared opposite the 
fovea of the right eye. The experimenter, who was seated 
at the observer's right, observed the latter's eye through a 
hand lens. A black box with a very narrow slit in one side 
was so arranged that the light from an electric bulb inside 
produced a bright point of light upon the cornea. The posi- 
tion of the box was shifted until the point of light fell upon 
the iris of O's eye near the edge of the pupil. When the eye 
shifted, the margin of the pupil moved noticeably nearer to 
or farther away from the dot of light, which remained approxi- 
mately stationary. For the practice series, a sheet of black 
cardboard was used with a horizontal and a vertical line cross- 
ing at right angles. Distances of 5 cm were laid off as units 
along each line. O looked at the fixation-point, then at some 
point along one of the lines, then again at the fixation-point. 
After practice, the experimenter was able to tell, with approxi- 



472 CLARK 

mate accuracy, from the appearance of the eye, over how great 
a distance upon the cardboard the observer's glance had passed 
in a vertical or a horizontal direction. From the list used in 
the experiments of Chapter II, we selected the words which 
had aroused images differing but slightly from the pure types. 
The selection was made so that the proportion of images in 
each of the three classes should be approximately the same. 
Sixty-nine words 23 were pronounced for A, while only the 
first 35 were used for B. The instructions were those of the 
preceding experiments with the following additions : " You 
are to fixate the white dot upon the black screen. When a 
visual image appears, try to keep it constant, but, if it dis- 
appears, do not make an effort to recall it. You are to start 
the stop-watch when the image first appears, and to stop it 
when the image finally disappears." After the observer had 
given his account of the image, he was questioned as to any 
points which he had overlooked. The experimenter sought 
complete information concerning (i) the visual background 
of the imaged object, (2) its size and (3) details, (4) somatic 
reference, and (5) accompanying kinaesthetic processes. 

Results. Table V gives a general tabulation of the images 
of observers A and B. 

Some visual-verbal images occurred, but they are not included in 
these results. Reports are not included under every heading for every 
image, since in some cases the image would shift, or O would be uncer- 
tain as to an introspective item. The percentages are based upon the 
numbers tabulated. 

As regards the nature of the different sorts of image, these 
results are, on the whole, in accord with those of the experi- 
ments already recorded. F-images and U-images generally 
had a scenic background, while, with G-images, an imaged 
visual background was either only a haze or was altogether 
lacking. In F-images the details were usually numerous and 
clear. This was less often the case with U-images. G-images 
were more apt to have few and vague details than were those 
of either of the other groups. Somatic reference was char- 
acteristic of F-images, while it did not seem to be present 
with the other kinds. In this experiment, U-images seemed 

23 The list of words was as follows : sword, soap, ogre, leaf, ghost, 
orange, nymph, broom, pin, oracle, cat, tomato, druid, pipe, catacombs, 
horse, key, hamlet, convent, church, Marmion, lyre, snake, banana, ice, 
centaur, aeroplane, mirror, child, knife, serf, dungeon, stone, gun, 
tournament, boat, cloak, river, w r agon, nail, tiger, helmet, coin, witch, 
moat, grave, wand, rose, dog, coat, cloud, ring, lion, grass, lemon, sled, 
hand, bag, chimney, purse, griffon, temple, shoe, Holy Grail, vase, 
Jupiter, sultan, shrine, Nile. 



VISUAL IMAGERY AND ATTENTION 



473 





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474 



CLARK 



the most likely to be exaggerated or dwarfed. This was less 
often the case with G-images and it seldom occurred with 
F-images. Ocular movements and sensations of ocular strain 
seldom occurred in connection with G-images, but were fre- 
quently noticed with the other varieties. Table VI shows the 
number and the extent of ocular movements. Although these 

TABLE VI 





Average 
number of 
movements 
per image 


Average 
extent of 
movement 

(in cm.) 


Right to Left 


Left to Right 


Up or Down 




Total 
No. 


Ex- 
tent 


Total 
No. 


Ex- 
tent 


Total 
No. 


Ex- 
tent 


F-images 


1.84 


5.64±2.9 


13 


4.66 


13 


7.11 


8 


3.75 


U-images 


1.33 


5.15±2.4 


6 


3.33 


9 


6.44 


1 


2.5 



movements were more frequently present with U-images than 
with F-images, the average number of movements per image 
was less and the extent was less in the former case than in 
the latter. " Extent " refers to the distance, as on the card- 
board screen, over which the glance of the observer was esti- 
mated to have passed, not to the amount of movement of the 
eye-ball. Complete data concerning the duration of the images 
cannot be given, since 18 of the 33 G-images were immediately 
followed by F-images. In such cases, the duration of each 
could not be accurately determined. In 52 instances, how- 
ever, the time-interval could be ascertained. These results are 
shown in Table VII. F-images and U-images were, in gen- 
eral, longer than G-images. The significance of the figures 
is dubious, however, because of the wide variations in time. 





TABLE VII 








Number 


Average 
duration 


M. V. 




23 


24.0 sec. 


13.6 








35 


10.8 sec. 


8.1 








14 


26.8 sec. 


12.0 







The fact that F-images and U-images are longer than G-images 
might account in some measure for the occurrence of ocular move- 
ments with the two former classes and their absence in other cases. 
The eyes might tend to move because there was long fixation, regard- 
less of the nature of the accompanying image. The time-interval 



VISUAL IMAGERY AND ATTENTION 475 

could not, however, be the sole factor involved, for ocular movements 
occurred with some very short F- and U-images, and did not occur 
with G-images which were considerably longer. Ocular movements 
occurred toward the end of 6 images which lasted longer than 15 sec, 
but in 3 cases other movements had also occurred toward the beginning 
of the period. 

The results of this experiment seem to indicate that some 
relation obtains between ocular movement and different sorts 
of image. The existence of such a relation may seem strange 
in view of the results of our earlier experiment, which showed 
that, when grouped according to characteristics, there are few 
images of any pure type, each class tending to merge into 
the others. But the correspondence may be due to the fact 
that the amount of ocular movement accompanying any visual 
image is related to its general setting, rather than to the 
definite patterning of characteristics, which, as we have seen, 
varies considerably within the groups. It is possible that 
different characteristic motor attitudes or general conditions 
of the organism occur with F-images, G-images, and U-images, 
and that these attitudes involve certain reactions upon the 
ocular muscles. The fact that kinaesthetic sensations or images 
were reported in a comparatively small number of cases would 
not necessarily invalidate such a conclusion. The attention 
of the observer was directed toward the visual image, and the 
effects of muscular strain or movement might easily have been 
overlooked. The experimenter purposely refrained from all 
unnecessary emphasis upon this aspect of the problem in order 
that conditions might be as natural as possible. 

Experiment 2 
Problem and apparatus. It occurred to the writer that the 
results of Experiment 1 would be more significant if con- 
firmed by investigations involving an objective record of 
ocular movements. It also seemed advisable to try to find the 
particular factor or factors which were most closely connected 
with ocular movement, instead of resting content with the dis- 
covery of the association of such movement with certain kinds 
of imagery. These were our chief purposes in the present 
experiment. For recording ocular movement, we employed 
the writing tambour of the laryngeal recorder described by 
Krueger and Wirth 24 which was connected by rubber tubing 
to the nystagmograph of A. Schackwitz. 25 A record of the 

24 Psychol. Stud., 1905-06, i, 103. 

26 Zsch. f. Psychol, 1913, lxiii, 442. When the spectacle-frame to 
which the tambour was attached proved to be unsatisfactory, we re- 
moved the tambour and fastened it to a support made of a system of 
adjustable rods and attached to the head-rest 



476 CLARK 

time in seconds was kept by means of an electric marker actu- 
ated by a metronome, or, in the later experiments, by a time- 
clock. A second pneumatic system was used to record the 
course of the image. For this purpose a rubber bulb was so 
fitted into a cardboard frame that O could produce variations 
in the height of the recording line by changing the degree of 
piessure upon the bulb. Strong pressure meant a high degree 
of clearness in the imaginal processes. 

Method. C, D, and'E served as observers. The observer 
was seated with his eyes closed and his head fixed in a head- 
rest. The first pneumatic system was inflated, and the small 
tambour of the second system, adjusted to the head-rest, was 
placed against the right eye-lid. Movements of the eyes were 
thus automatically recorded beside the clearness-line upon the 
kymographic paper. The instructions were as follows : ''After 
a signal ' ready ' a word will be pronounced. If a visual 
image appears, try to hold it constant, but do not recall it 
when it disappears. With the right hand, compress the bulb 
when the image appears. Increase the pressure whenever the 
image grows clearer and diminish the pressure whenever the 
image becomes less clear. After the image has disappeared, 
you will be interrogated as to (i) shifts in attention from 
object to object, (2) changes in the clearness, the intensity, 
and the content of the imaginal object, (3) associative pro- 
cesses, (4) somatic reference, (5) the visual background of 
the image, (6) specificity of the imaged object and its tem- 
poral and spatial relations, and (7) familiarity." Sixty-three 
words were used with each of the three observers. 26 

Results. Nothing of importance resulted from this experi- 
ment in respect to the characteristics of the different sorts of 
images. The descriptions are in general accord with the 
more detailed accounts discussed above. The results are sig- 
nificant, however, in that they show an appreciable corre- 
spondence between fluctuations in the clearness of the imagery 
and ocular movements. The records were divided into 5 
classes according to the degree of correspondence. We de- 
scribed a record as showing no correspondence when one line 
fluctuated and the other did not, or when there were striking 
differences in the number and the position of fluctuations. 
Figure 1 shows typical examples of the records in which there 
was correspondence. Records I, 2, and 3 are samples of high 
correspondence, record 4 of close correspondence, while in 5 

26 Some of the words were as follows : pickle, wizard, maypole. 
shell, moat, Hercules, shepherd, thimble, rainbow, scythe, commence- 
ment, dell, note-book, Scotchman, Cinderella, mouse. 



VISUAL IMAGERY AND ATTENTION 



477 



Fig. i 




478 



CLARK 



the resemblance of the lines is general, and in record 6 the 
correspondence is limited. Table VIII shows the classification 
of the results for each observer. 



TABLE VIII 





Amount of Correspondence 




None 


Some 


General 


Close 


High 


Totals 


c 


17 


8 


24 


6 


10 


65 






D 


17 


21 


9 


5 


8 


60 






E 


10 


19 


7 


7 


4 


47 






Totals 


44 


48 


40 


18 


22 


172 














128 







In 128 of the 172 cases, there appeared, then, a correspond- 
ence between the records for fluctuations of the clearness of 
the image and the records for ocular movements. This agree- 
ment is the more striking in view of the fact that very slight 
variations in the adjustment of the apparatus or in the time 
of O's response in varying the pressure upon the recording 
bulb might have changed the records in such a way that a 
correspondence which really existed would have been obscured. 



Experiment 3 

Problem and apparatus. In all of the preceding investiga- 
tions, the images evoked differed widely in their nature and 
in their origin. Some were very schematic, while others pre- 
sented many specifying details. A considerable number re- 
ferred to recent experiences, but some were related to habit- 
ual perceptions, and still others symbolized classes of objects. 
In view of these facts, it seemed advisable to investigate the 
occurrence of ocular movement in connection with images 
resulting from similar perceptions. We decided to employ a 
series of objects which were homogeneous except in respect 
to meaning, and to note whatever differences in ocular move- 
ment might occur when the objects were imaged. For this 
purpose, we devised a series of thirty sense and nonsense 
figures. Each figure or diagram was cut from white paper 
and pasted on a black card 5 inches square. Half of the 
pictures represented meaningful objects, while the others were 
intended to be meaningless. 



VISUAL IMAGERY AND ATTENTION 



479 



Ocular movements were detected by a method different 
from the methods used in our previous investigations. In 
Experiment i, changes in the position of the eye had been 
observed by the experimenter; in Experiment 2, a mechan- 
ical device had been employed. In the following series, the 
observer himself reported the occurrence of ocular movement. 
Our plan was to place before the observer a set of points of 
light arranged in such a way that, when fixation was steady, 
all of the lights would fall upon the blind-spot. A slight 
movement of the eye, however, would bring some of the bright 
points within the field of vision. 27 The apparatus (repre- 
sented in Figure 2) consisted of two black metal light-boxes 
designed for the investigation of indirect vision. The smaller 
light-box supplied the fixation-light and the larger box the 
lights for determining the limits of the blind-spot. Rotating 
discs upon the face of the larger box provided for a radial 
series of light-spots, 5 mm apart, along any one of 360 
diameters. 




Method. C, D, and F served as observers. The observer 
was seated in a chair with his head fixed in a head-rest and 
his right eye covered with a black cloth. His left eye was 
at a distance of i}/ 2 meters from the face of the small box, 

27 Perky {op. cit., 437) employed a similar method. Our arrange- 
ment provides for the detection of considerably smaller movements of 
the eyes and also for a nice control of the position and intensity of 
the light-spots. 



480 CLARK 

and the point of light at the intersection of the two lines of 
holes appeared opposite the fovea. This dot served as a fixa- 
tion-point; the other openings were covered. Light was ad- 
mitted through apertures successively nearer to the center of 
the face of the large light-box until those points were found 
which cast beams of light just within the area of the blind- 
spot. As a check upon the accuracy of the adjustment, the 
slide and the disc on the small box were so moved as to 
admit light through apertures 5 mm above or below, and at 
the right or the left of the original fixation-point. When either 
of these four adjacent spots was fixated, some of the points 
of light on the large box became visible. An extremely slight 
change in the position of the eye, then, brought the lights 
partially within the field of vision. 

Before each experiment, the head-rest and the boxes were 
adjusted with reference to O's blind-spot, since a different 
arrangement was necessary for each observer. When O had 
taken his place in the dark room, he was given the following 
instructions : " You will be shown a series of four drawings, 
the experimenter naming each one as it appears. 28 Shortly 
after a ' ready ' signal, a drawing will be exposed for 20 
seconds. After a further interval, of 20 seconds, another will 
be exposed, and so on." The drawings were placed over the 
fixation-point of the small box and were illuminated from 
above. During this part of the experiment, the apparatus 
was concealed by a black screen with an opening (2"xi/ 2 ") 
through which the card was visible. After the perceptual 
series, the observer was instructed as follows : " You are to 
fixate the single point of light. The experimenter will pro- 
nounce the names of the drawings, and you are to call up a 
visual image of each. Try to hold the image constant, but, if 
it disappears, make no effort to recall it. Press the key 
when the image appears and release and press it whenever 
the lights at the side become visible. Release the key and 
say ' now ' when the image disappears. Then give complete 
introspections for the period of the image." A kymographic 
record was made showing the appearance and disappearance 
of the lights as indicated by O. The experimenter timed each 
image with a stop-watch. During the last half of the series, 
each record was made for a period of 20 seconds, and the 
observer was required to recall the image if it disappeared 
during that time. Several other records were made as con- 

28 The following names were given to the figures: wij, bottle, ked, 
butterfly, fak, turtle, ged, star, pam, spool, tis, daisy, rel, key, bam, fish, 
hof, ring, lat, apple, zum, Jeaf, doj, cup, mej, knife, dak, pipe, kif, 
scissors. 



VISUAL IMAGERY AND ATTENTION 481 

trols with each observer. Under the controls, O was told 
to fixate the point of light until the experimenter gave a signal 
to stop at the end of 20 seconds. Under these conditions, no 
attempt was made to arouse imagery. After each experi- 
mental period O's descriptions were transcribed from his 
dictation. When necessary, the experimenter questioned him 
with respect to (1) the kinds of conscious processes integrated 
with the total visual image, (2) associative processes, (3) 
the clearness of the image, and (4) the accompanying affec- 
tive tone. O was then asked to sketch the object as perceived 
and also as imaged. 

Results. Although the drawings did not serve the purpose 
for which they were primarily intended, the results were sig- 
nificant in other respects. Most of the pictures devised for 
nonsense drawings either proved to be meaningful or were 
accompanied by meaningful associative processes. Only 7 
of the 88 images had no meaning for the observer or signified 
simply " drawings-shown-a-few-minutes-ago." There was no 
appreciable correspondence between images of this sort and 
the presence or absence of ocular movement. The experiments 
did, however, supplement the results of the investigations 
which were mentioned in Section II with respect to the size 
and the accompanying affective tone of the image. 

We have already cited a possible objection to the observer's repro- 
duction of the image by a drawing. Since kinaesthetic and tactual 
sensations were involved in such a depiction, it was possible that the 
results were not exact representations of the images. But even if 
allowances are made for constant errors, the total results seem sig- 
nificant. 

Since the drawings were 13/2 meters away, we might expect 
the observer's representations to be slightly smaller than the 
originals. There was, however, a strong tendency, with two 
observers, to exaggeration in the image. No drawing was 
smaller than the figure by more than an inch, while 7 exagger- 
ated it by 1-6 inches. 

All observers reported a predominance of pleasantness over 
unpleasantness in the images (43:19). As a rule, however, 
the affective tone was connected with the free or impeded 
fulfillment of instructions, not with the character or the sig- 
nificance of the total images. Too often writers have assumed 
without warrant that coincident affective tone and image 
were inherently related. 

The correspondence between ocular movement, the sort of 
image, and the condition of attention appears when we compare 
all the results obtained from the three observers. The num- 



482 



CLARK 



ber of images associated with ocular movements is shown in 
Table IX, and the duration of these movements with any 



TABLE IX 





C. 


D 


F 












I. 


Co. 


I. 


Co. 


I. 


Co. 


Ocular movement 


29 


4 


7 


4 


28 


3 






No ocular movement 








23 


1 


1 






image, in Table X. (I. stands for the period of the image; 
Co., for that of the control). Not only did D have fewer 
images accompanied by ocular movement than did C or F, 



table x 

Duration of Ocular Movement 



Second 




2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


13 


15 


20 






D 


I 






1 






2 


1 












3 


Co 
























1 


3 




I 


1 


5 


4 


4 


2 


8 


2 




2 






1 


C 






Co 






1 


2 




1 












I 


1 




3 


1 


2 


7 


1 


2 


4 


1 


2 




4 


F 






Co 




1 








1 






1 











but the number of movements with a given image was apt 
to be less in his case. There was also a noticeable difference 
in the general character of the images of the three observers. 

(i) The size of D's images, according to his drawings, varied but 
slightly from that of the diagrams, while both C's and F's images 
were exaggerated in approximately 68% of the cases. 

(2) None of D's images were incomplete, but 11 of C's and 15 of 
F's lacked some or many details. 

(3) Four of D's images, 8 of C's and 9 of F's revealed inaccuracies 
of detail. 

(4) Three of C's images and 6 of F's were of objects other than the 
diagrams. Four times, in the case of F, these representations were 
incomplete. D was always able to arouse an image of the perceived 
drawing. 

(5) D's total images never contained imaginal visual elements which 
were not represented in the corresponding perceptual objects. No pro- 
cesses from other sense departments were intimately integrated with 
the images. Such integration occurred with 5 of C's images. Four 
times the added elements were visual, and once they were kinaesthetic. 



VISUAL IMAGERY AND ATTENTION 483 

In 14 instances, F's total images were elaborations of the perceptual 
object. The added elements were visual in 3 cases, kinaesthetic in 8, 
tactual in 2, and organic in one. 

(6) D always drew the same diagram as representing both the image 
and its corresponding percept. This was the case with only 11 of Cs 
images and with none of F's. 

Individual differences were noticeable, not only in the char- 
acter of the image, but also in the state of attention. 

(1) In the case of 22 of D's images, there were a few (from one 
to three) simple groups of associative processes, usually secondary 
(verbal). Twelve of Cs images and 19 of F's either lacked such pro- 
cesses or were accompanied by a great many. Attention was apt to 
fluctuate when associative processes were so numerous as to act as 
distractions or when the absence of these processes made the images 
uninteresting. 

(2) Further differences existed with respect to the degree of clear- 
ness and its fluctuations. Over half of D's images were very clear 
and steady. Twenty of Cs images were very clear, but 19 of them 
fluctuated. Moderate clearness was characteristic of 15 of F's images, 
and fluctuations occurred in 24 cases. 

(3) D's attention was less frequently secondary (or active) than 
was Cs or ,F's. D reported a conflict between groups of processes, 
or attention with effort, 6 times, C 11 times, and F in 9 cases. 

In brief, fixation was usually steady when an image was 
very clear and did not fluctuate, when it was accompanied by 
few associative processes, and when attention was without 
effort. Under other conditions ocular movement tended to 
occur. 

The dissimilarities among the images of a single observer 
are associated with ocular movement in the same way as are 
variations in all the images of different observers. 

In the six cases in which D's attention was secondary, fixation was 
unsteady. During the course of 4 other images the eyes moved, al- 
though attention was without effort, but in all of these instances there 
were many associative processes or irrelevant ideas. The one image 
which was noticeably vaguer than any of the others was also accom- 
panied by ocular movement. All of Cs images were accompanied by 
movements of the eyes, but the one image with which there was only 
a single movement in 20 seconds was very clear and constant, and 
attention was without effort. One of F's images was accompanied by 
no ocular movement. Attention was without effort, and the image was 
clear and constant. With 4 of his other images, there was only one 
movement in 20 seconds. In all of these cases, attention was without 
effort. Two images were very clear, and the other 2 were moderately 
clear, while the images remained constant or fluctuated but slightly. 

If we turn to the kymographic records of the control-experi- 
ments, we see that they are in accord with the results already 
mentioned. Ocular movement frequently occurred during the 
controls, and, when it did, the general conditions of conscious- 
ness closely resembled those which were characteristic of the 
images accompanied by ocular movement. 



484 CLARK 

To sum up, we may say that there is usually no movement 
of the eyes with images which are fairly faithful representa- 
tions of the corresponding perceptual objects ; while ocular 
movement tends to occur with images which differ from the 
perceptual objects in size, and in completeness and accuracy 
of detail, and, in some cases, when processes from other sense 
departments are integrated with the images. Moreover, fixa- 
tion is apt to be steady when there are few associative pro- 
cesses (but not so many as to distract attention from the 
image and not so few as to allow attention to wander), when 
the image is clear and stable, and when attention is without 
effort. When these conditions do not exist, ocular movements 
tend to occur. 

The results of Experiment 3 are in general accord with those of a 
preliminary series in which C alone served as observer. The apparatus 
was a rough wood and cardboard model like the metal boxes in all 
essential details. A series of words was used to arouse images. O was 
required to time the images with a stop-watch and to press a record- 
ing key whenever the points of light became visible. During the course 
of 15 of the images, a beam of light was thrown upon the cornea of 
O's eye as in Experiment 1. Unfortunately, the light had to be of 
such a low intensity that the experimenter's observations of ocular 
movement are not reliable. The experimental conditions, especially 
the presence of the beam of light, distracted the observer. For this 
reason, the value of the results might be questioned if they were not 
in agreement with those of the other series. 

Records of 22 images were obtained. Two of these were U-images, 
13 were G-images, 7 were F-images. Of the F-images, 6 had somatic 
reference, 5 had a recognized scenic background, and 3 had fairly 
many associations. Of the G-images, none had a scenic background, 
and 11 had few or no associations. Ocular movements were reported 
by the observer with 5 (71%) of the F-images and with 7 (54%) of 
the G-images. 

As regards attention to the image, there was no ocular movement 
in the one case in which the image was very clear and constant, or 
with another image which showed a gradual decrease in clearness. 
Ocular movement occurred 1, 2, or 3 times in 5 of the 10 cases in 
which the image was vague but exhibited no appreciable shifts in 
clearness, and in 8 of the 10 cases in which there were marked fluc- 
tuations in the clearness of the image. There was evidently a degree 
of correspondence between the frequency of ocular movement and the 
kind of image, and a rather marked relation of ocular movement to 
attention. 

Experiment 4 

Problem and method. While Experiment 3 was in progress, 
it occurred to the writer that, in spite of the apparent accuracy 
of the apparatus, the observer might sometimes be unaware 
of the spots of light even when the eyes moved. If O's atten- 
tion were focused upon the visual image, there was a possi- 
bility that the light might fall upon a sensitive portion of the 



VISUAL IMAGERY AND ATTENTION 485 

retina without touching off a report. To test this hypothesis, 
we combined the methods of Exps. 2 and 3. With the left 
eye, the observer fixated the single point of light as in the 
preceding investigation. The right eye was closed, and the 
tambour used in Exp. 2 was adjusted against the lid. In 
general, the procedure was the same as in Exp. 3, except that, 
instead of exposing the drawings in a perceptual series and 
later arousing the corresponding images, a number of words 
were used as in Experiment 2. C, D, and F again served as 
observers. As a preliminary control, before each record was 
made, the observer intentionally moved his eyes. In all of 
these cases the movement was recorded and the dots of light 
became visible. Each record was taken for a period of 20 
seconds, as in the latter part of Exp. 3. 

Results. Six records were made with D as observer, 5 with 
F, and 8 with C. In D's case, no ocular movement was 
detected by either method. The dots were never visible during 
the 20 seconds of fixation, and the record made by the pneu- 
matic system showed no fluctuation. During the course of 
4 of F's 5 images, dots became visible, but the other recording 
line did not waver. Very slight ocular movements evidently 
sufficed to bring the dots within the field of vision, but were 
not large enough to affect the tambour. One of C's records 
indicated that the dots became visible 5 times while there were 
no corresponding fluctuations in the other line. In the other 
7 cases, ocular movement was indicated by both lines. There 
was a general conformity between the two records, although 
in some cases the record made by the pneumatic system indi- 
cated more fluctuations than the other line. 

There are several possible explanations of these apparent incon- 
sistencies. (1) C sometimes saw the points of light 8 or 10 times in 
20 seconds. It is very likely that she did not react quickly enough to 
record all the changes. (2) A twitching of the right lid might have 
changed the one record, although the eyes themselves remained steady, 
so that no dots appeared. (3) Where the excursion of the eyes was 
fairly wide, a fluctuation in the pneumatic record might have occurred 
when the projection of the cornea crossed the bulge of the tambour, 
and again when the eye resumed its original position, although the 
dots were visible but once. While one record was being made, the 
electric current was accidentally reduced, and the points of light 
became very faint. It was probably due to this fact that the dots 
were visible less often than in the previous periods. 

The results of this experiment seem to indicate that the 
suggested hypothesis is incorrect. If O's eyes had moved 
while he failed to notice the points of light, the pneumatic 
record would have fluctuated, while the other was unaffected. 
But this was not the case. When movement was recorded 



486 CLARK 

by only one line, it was the record made by O that showed 
fluctuations. The pneumatic system seemed the less accurate 
of the two. When slight movements of the eyes occurred, 
the observer noticed the dots, but the tambour was apparently 
not affected, while larger movements were recorded by both 
systems. 

From the results of Exp. 4 we infer that the perception 
of the dots of light during the experimental period indicated 
actual movement of the eyes. The results of the short trial 
preliminary to Exp. 3 revealed the same correspondence be- 
tween F-images and G-images which was discovered in Exp. 
1. Ocular movement usually occurred with the former images, 
but not with the latter. In Exp. 3, we found that the amount 
of resemblance among imaged objects and the corresponding 
perceived objects seemed to be connected with ocular move- 
ment. As has already been suggested, this correspondence 
may reasonably be referred to an association of ocular move- 
ments with certain conditions of attention. Both Exp. 3 and 
the preliminary trial confirm the correspondence of ocular 
movements with the degree of clearness and fluctuations of 
attention which was the most significant discovery in Exp. 2. 
In Exps. I and 2, the arousal of a particular image was not 
required, and the experimental conditions did not seem to 
impose any tax upon the observers' ability to hold the atten- 
tion steady. In Exp. 3, however, there occurred, as a result 
of the exacting instructions, numerous cases of secondary 
attention. There proved to be a positive correspondence be- 
tween this sort of attention and ocular movements. 

Were we to attempt an explanation of the correspondence 
which we have discovered between different sorts of image, 
attention, and ocular movement, we should turn naturally to 
the facts of perception. A series of special experiments would 
be necessary fully to substantiate a transfer of general motor 
attitude or of ocular movement from perception to visual 
imagery. Our results suggest, however, that there are sev- 
eral possible likenesses among perceptions and images in re- 
spect to movements of the eyes. 

(1) When an extended perceptual object close at hand has 
many details, we must, in order to gain an accurate im- 
pression of it, glance now at one portion, now at another. In 
a similar way, we have frequently discovered ocular move- 
ment and shifts of attention where an imaged object is rich 
in detail or is accompanied by numerous associative processes 
(as was the case with many of the F-images and with some 
of the images of drawn figures in Exp. 3). 



VISUAL IMAGERY AND ATTENTION 487 

(2) When a perceptual object has very few details, we are 
apt to grasp its significance at a glance and then to turn our 
gaze and our attention to something else. A similar tendency 
was manifested, in our experiments, in the case of some un- 
interestingly simple images. 

(3) In perception, when an object lacks cognitive clear- 
ness, our eyes are often focused first on one part, then on 
another, in order to gain a more definite impression. Such 
waverings of the glance were also characteristic of images. 

(4) Under normal conditions, when we attend successively 
to different aspects of a perceptual object, our glance almost 
invariably follows the direction of our attention. We have 
already given instances of the agreement between fluctuations 
of clearness and shifts of fixation in imagery. 

(5) Finally, when two rival objects claim the perceptual 
attention, the glance is apt to waver between them. Our 
results showed that secondary attention to imagery also in- 
volved ocular movements. All of these resemblances seem to 
point in the same direction. In the absence of contradictory 
evidence we may, then, reasonably suppose that the relations 
existing between the character of the object, attention, and 
ocular movements in perception are transferred to analogous 
cases of imagery. Such an hypothesis is in harmony with the 
current view of the physiological functions underlying per- 
ception and imagery. When an object formerly perceived is 
imaged there occurs, presumably, through central excitation, 
a reinstatement of the appxoximate physiological conditions of 
perception. The imaged object presents much the same color, 
shape, size, and details as does the perceptual object. There 
might easily be a similar reinstatement of muscular innerva- 
tions. In fact, the recurrence in imagery of the movements 
of the eyes involved in perception is a more probable phe- 
nomenon than is the accurate repetition of the visual details 
of the perceived object, since ocular reactions which are alike 
(at least in their gross characteristics) occur with a large 
number of perceptions, while a comparatively small number 
of objects present a close resemblance in their qualitative 
aspects. That is to say, there may be more likelihood of 
the integration of generic muscular reactions in imagery than 
of the formation of generic visual images. 

IV. Summary and Conclusions 

The results upon which we base our conclusions were ob- 
tained from six trained observers, four of whom served in 
two or more of the four principal experiments. The ocular 



488 



CLARK 



movement occurring in connection with visual images was 
recorded in the various investigations by three different meth- 
ods. There was a general agreement in the results whenever 
two or more experiments involved the same problems. Al- 
though individual differences were sometimes conspicuous, they 
were of such a sort as to substantiate our conclusions, not to 
invalidate them. 

Agreement between our results and those of other investi- 
gators is as close as we could reasonably expect in view of 
the differences which obtain in instruction and method, and, 
especially, of the differences in the criteria used for classi- 
fying images. (See Table XI). The "memorial image" of 



TABLE XI 

Specific Reference 



Clark 
Perky 

Ogden 
Koffka 



F-Images 



Memory 
(part, and 
pers. ref.) 



Memory 
(fam.?) 



U-Images 



Imagination 



Individual Individual 

(degrees of ind'ing and loc'ing) 



Generic Reference 

G- Images 

Imagination 



General 
(in part) 



both Ogden and Perky should probably be considered as a 
sub-class of our F-images. Perky's images of imagination 
we should generally have classed — so far as we can tell from 
her descriptions — as G-images ; Ogden's images of imagina- 
tion, 29 as U-images. We found that our G-images (Perky's 
imaginations) 30 and our U-images (Ogden's imaginations) 
were usually unlike in most of their characteristics. It is not 
strange, then, that there should be considerable disagreement 
between Perky's and Ogden's results when these two classes 
are compared. Koffka's general images would coincide in 
part with the G-images of our classification, while his indi- 
vidual images would include both our F and U classes. 

i. Five of the characteristics of images which we have ex- 
amined were also considered in much the same way by 

29 Ogden appears to have left his observers free to apply their own 
criteria to their images : he says, " The criteria which seemed to be em- 
ployed primarily by our observers were those of ( familiarity ' and ' un- 
f amiliarity '" (p. 384). 

30 Perky writes of " generic images " and of " habitual imagina- 
tions " (pp. 440, 447) in contrast to "particular images." 



VISUAL IMAGERY AND ATTENTION 489 

Perky, Martin, and Ogden. The following summary gives a 
comparison of the results. 

(a) There was a general agreement in respect to associa- 
tive processes, which frequently accompanied the memorial 
images of Perky, 31 Martin, 32 and Ogden, 33 and were found 
with our F-images, and also with Ogden's images of imagina- 
tion and our corresponding U-images. With Perky's 34 and 
Martin's 35 images of imagination and with our corresponding 
G-images these accompanying processes occurred less often. 

(b) Three of the four investigations indicated similarities 
of clearness and of detail. The memorial images of Ogden 36 
and of Martin, 37 and our F-images, were apt to be distinct, 
not " scrappy "■ and " filmy," as were Perky's. Instead of 
being " substantial " and " complete," as were Perky's images 
of imagination, 38 our corresponding G-images often presented 
few and vague details. Many of Ogden's images of imagina- 
tion 39 and of our U-images were, detailed and clear. 

(c) The results of Ogden 40 and of Martin 41 also agree with 
ours in failing to show any correspondence between the kind 
of image and the presence or absence of color. Perky gives 
no statistical summary, but describes the images of memory 
as " colorless etchings," and those of imagination as " often- 
times, on the contrary, very highly colored." 42 Her state- 
ments, however, appear to be contradictory, for she also states 
that the images of memory " retained their daylight char- 
acter," while those of imagination took the illumination of 
their surroundings. 43 This statement might be interpreted as 
meaning that it was the memories that were colored and the 
imaginations that had no color of their own. 

(d) The results of Ogden's investigation and of our own 
do not agree with Perky's with respect to affective tone. 
Ogden 44 found no evidence of Perky's memorial " mood of 
recognition " or. imaginative " mood of surprise." In our in- 
vestigation, the images (especially in the F class) were fre- 
quently pleasant, but an explicit feeling of familiarity was 
not always found with F-images, and a feeling of strange- 
ness or surprise occurred with only two U-images. 

(e) As regards stability, there is no correspondence of 
results. Perky's memorial images were described as " scrappy 
and fleeting," 45 her images of imagination as " substantial." 46 

81 Perky, p. 451. 32 Martin, p. 408, 412. 33 Ogden, p. 405. 

34 Perky, p. 450. 35 Martin, p. 408, 412. 36 Ogden, p. 398. 
37 Martin, p. 400. 38 Perky, p. 451. 39 Ogden, p. 398. 
40 Ogden, p. 396. 41 Martin, p. 405. 42 Perky, p. 447. 

43 Perky, p. 446. * 4 Ogden, p. 398. 45 Perky, p. 447. 
48 Perky, p. 451. 



490 CLARK 

Martin's images of memory were usually, though not always, 
more stable than those of imagination; 47 and Ogden found 
about the same number of stable images of his two kinds. 48 
Our investigation revealed no significant correspondence be- 
tween the kind of image and its stability. Where a com- 
parison is possible, the total results of Ogden and Martin 
agree, in general, with those of the writer, while all of these 
three investigations give evidence which is contradictory to 
that of Perky. 

2. As regards ocular movements, our results agree with 
Perky's in so far as these movements usually occurred with 
her images of memory and frequently with our larger class 
of F-images, but were not, as a rule, reported with her images 
of " imagination " or with our corresponding G-images. The 
frequent occurrence of movement with our U-images, how- 
ever, suggests that no essential relation obtains between images 
of " memory," as contrasted with other forms or functions 
of imagery, and these kinaesthetic processes. That is to say, 
the conditions of ocular movement with imagery seem to be 
general conditions, — not the conditions which distinguish two 
imaginal functions, memorial and imaginative. Indeed, it is 
doubtful whether it is feasible and proper to attempt to oppose 
these two functions at the level of the total image. Our own 
analyses, as well as those of Koffka, suggest, instead, a very 
large number of functional gradations for the simpler imag- 
inal complexes ; — gradations of specifying, of individualizing, 
of generalizing, of symbolizing, and of reference to the ob- 
server, to objects, to times, to places, and to contexts. The 
alleged functional distinctions based upon " particularity " 
and " personal reference " are gross, and, moreover, we are 
not persuaded* by the facts that they are correlated with such 
differences in process and integration as temporal course, 
clearness, substantialness, and affective and organic accom- 
paniments. As for the presence and absence of ocular move- 
ments under imagery, we are not certain that familiarity, " the 
mood of memory" (Perky, p. 451), is essentially connected 
with this special kinaesthesis ; while we have failed to discover 
by introspection an antithetical or contrasted mood of un- 
familiarity or " novelty " to mark the absence of such move- 
ments. These specialized movements we are inclined to ac- 
count for in another way. They seem to us to be symptomatic 
of those general central conditions which underlie determina- 
tion and which fix the state and the configuration of conscious- 

47 Martin, p. 407. 48 Ogden, p. 404. 



VISUAL IMAGERY AND ATTENTION 491 

ness, — i. e., fix attention and associative completion. 49 When- 
ever these general conditions approximate or tend to repro- 
duce the usual psychophysical accompaniments of visual per- 
ception, then the ocular movements also tend to occur. Visual 
perceptions normally flow in trains, passing from feature to 
feature of the object and likewise from object to object. The 
kaleidoscopic change of clear processes bears with it a suc- 
cession of ocular movements. We believe that whenever this 
diffusive and exploratory kind of visual attention occurs, 
whether or not the organism is immediately affected by a 
visual stimulus, there normally appear, save under some 
special inhibition, the small movements of the eyes which 
have now been detected in many experiments set for the 
study of imagery. 

If our view is correct, then the presence and frequency of 
ocular movements would have no immediate or intrinsic con- 
nection either with familiarity or with " personal reference " 
and " particularity ;" though it might well be true that those 
images which make most explicit reference to the observer 
and to his past experiences also most frequently fulfill the 
general conditions just referred to. 50 It follows that isolated, 
detached, unset and un-detailed objects, such as appeared in 
our G-images, would least reinstate the usual conditions of 
perception ; but it does not follow that these objects furnish 
the materials of " imagination." We are thus led to connect 
ocular movements more directly with general central and con- 
scious conditions than with special functional differences dis- 
played by the image. 

In so far as it is permissible to base generalizations upon 
our experimental results, we feel justified in drawing the fol- 
lowing conclusions: 

i. If visual images are divided into three groups upon the 
basis of the presence or the absence of (i) specific reference 
and (2) familiarity of the object, certain other functional 
characteristics are found to be rather closely associated with 
a particular group or with groups of images. Pure types, 
however, are comparatively rare, and intermediate forms are 
relatively numerous. 

2. A correspondence discoverable between kind of image 

49 Perky found that attention wandered in memory but was nar- 
rowly focused in imagination (p. 449). 

50 As regards audition, olfaction, and the other senses, the facts are 
not sufficient to warrant general conclusions. Remembering the his- 
tory of the doctrine of " fluctuations of attention," the author is sus- 
picious of any general functional difference which does not take into 
account the bearing of sensory adjustments. 



492 CLARK 

and amount of ocular movement is probably to be referred 
to certain general conditions of attention. 

3. Changes in the clearness of the image correspond, to an 
appreciable extent, to movements of the eyes. 

4. Ocular movement is more likely to occur in secondary 
attention than in primary or derived primary attention. 

5. Characteristic ocular movements, and possibly general 
motor attitudes, seem to be transferred from visual percep- 
tions to visual imagery. 



VITA 

Helen Clark was born in Cortland, New York, in 1890. She 
prepared for college in the grades and in the State Normal 
School at Cortland, and was graduated from Vassar College in 
1913, with the degree of A. B. She was graduate scholar at 
the University of Illinois in 1913-14, and graduate fellow in 
1914-16. In 1914 and 1915, she was instructor in psychology 
at the State Summer School of Rutgers College. She has 
published (jointly) "A suggested coefficient of affective sensi- 
tiveness" (Amer. J. of Psychol., 1913, XXIV, 583), and has in 
press a research in social psychology upon 'The crowd." 




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